Telephone system



Dec, 30, 1924. i 1,5215159l A l H. D. MCPHERSON TELEPHONE SYSTEM Filgd Den. -22 1920 ll SheefcS-Sheet 1 Dec, 30, 1924,.

1,52Lf159 H. D. MaCPAHERSON TELEPHONE SYSTEM Filed Dec. 2,2 11'920 11 sheetsPsheet 2 f I Hugh D /76/6/9/66/3'077 v H. D. MaCPHERSON 4 TELEPHONE SYSTEM Filed Dec. 22 192Q l1 Sheets-Sheet 4 MA GINAL mfg Mac Phew/7.

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Dec. 30, 1924- I 1,521,159

' H. D. MacPHERsoN TELEPHONE SYS TEM Filled Dec. 22, 1920 11 sheets-sheet v @I OFF/cf X arAGo//VG [f @l 736 T /nvenorf Hug/1 0. MacPherson Dec. 30, '1924. 1,521,159

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' H. D. MCPHERSON TELEPHONE SYSTEM Filed Dec. 22. 1920 ll Sheets-Sheet 9 UFF/c5 Y /034 /n Ven/Orr l Hay/7 0 MacPhero/v Dec, 30, 1924.

. 1,52L159 H. D. MaCPHERsoN TELEPHONE SYSTEM Filed Deo. 2:2;1920' 11 sheets-sheet 11 U0 /mp Huy/1 D. MacPhe/Jon flat-enticed Dec.

naar" rares HUG-li D. MnoPHERS-ON, OF SUMMRVNET JERSEY, ASSIGNOR TO WESTERN ELECTRC COMEANY, INCORPORATED, OF NEW YORK, N. Y., A, CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application sied December 22, 1920. serial No. 432,571.

To all w/Lomc't may concern."

Be 1t known that l, HUGH DONALD Maolji-innsoN, a citizen of the United Sta-tes, re-

siding at Summit, in the county of Union,`

State of N ew Jersey, have invented certain new and useful improvements in Telephone Systems, of which the followingl iS il fullf clear, concise, and exact description.

' This invention relates to improvements in switching systems wherein methods and means are provided for controlling the transn'rission of current'impulses for a plurality of trunk lines extending between widely separated otiices, and has particular reference to such methods and .means as applied to telephone systems. Y Y ln systems ,of this character, it has been proposed to employ, Yat opposite ends of a common signaling path, sending means for transmitting thereover, codes of current impulses, characteristic of the individual trunks and determined by the trunk line circuit which is temporarilyassociated with the common path forsignaling purposes.

lt isoften desirable to extend a connec- V tion from an originating office to some distant oflice through one of a plurality of intermediate or tandem offices, by means of a sectionalized trunk line circuit, the sections thereof being interconnected at the various tandems ofiices.

An object of this invention is to selectively `and automatically extend a connection from an originating office to terminate either at an adjacent ofiice or at some distant of- .tice which may be reached only through the adjacent ofiice, as well as to further extend the connection to another oflice located at a considerable distance which may be reached only through the adjacent and said distant oi'lices. lla either case, the selecting and operating current impulses are transmitted between the adjacent Voffices of the series over a common'signaling path for the trunk lines interconnecting such offices.

Itis also an object of the invention to y establish connections betweentwo offices by transmitting Acurrent impulses over a rpath' common to a plurality of `trunk circuits,

which kimpulses control the selection of idle trunl; circuits at an intervening office.

Another object isV to Vcontrol from one 'remain established.

A further object of the invention is to provide means whereby when a connection through intermediate offices requiring the use of amplifiers in the various sections thereof is selected, a properly balanced repeater is rendered effective and associated Y with each of the talking sections of the trunk circuit in response to the selecting impulses originating at the originating ofiice.

ln order to attain'these objects, in accordance with one feature of the invention, there is provided at the originating oilice, a plurality of terminals for each trunk line circuit leading to an adjacent office, a plurality of terminals also being provided thereat for each of the trunk line circuits leading toofiices adjacent thereto. The latter mentioned offices are also siniilarly equipped. Any of the terminals, whenv selected for use, causes the automatic association of the trunk with the common apparatus for transmitting codes of current impulses over the common signaling path leading to another ofiice to selectively control apparatus thereat.V The character of the codes of impulses are dependent upon the individual terminal of the trunk selected at the originating oi'lice and the apparatus which functions at the adjacent office will either cause the display of a signal thereat for connections terminating at such oiiiee or find an idle trunk circuit leading to another office and thereafter causes the association of such idle trunk with the common signaling path extending to the latter-mentioned ofiice. Another combination of impulses sentV from this common path selects appaiatus at the distant ofiice which, as before, may function to cause the display of signals i thereat or to further extend the connection to another oiiice for its termination.

tacts of relays 203and 205, the brush arm 204, the contact in :engagementtherewith,

the control conductor B10, the inner right? hand Vcontact* of relay 12, the winding of relay 35,*the right-hand contact of relay 25,

the outer right-hand alternate contact of relay 2dr, and the outer right-hand alternate contact ot relay-Sat to ground. Relay 35 in operating locks over a circuit including its right-hand contact and in opening its norinal contacts, disconnects ground fromY they Vbrush arm 207, the segment` 208, the o-uter right-hand alternate contact o'f'relay 201 and the winding ot release magnet SRM to ground. The attraction ot the armature Y ot the release magnet SRM, upon its energizatiou, releases the brush arm 207 which is thereupon rotated through a complete cycle at the end ot which cycle the brush 1s stopped in its normal position, as shown.

rlhe brush arm 207, in being rotated, irst engages the start segment 209, thereby con- -nectingpositive battery to the common signaling conductor l? leading` to the oliice X. rthe brush then moves out ot' engagement with the segment 208, opening the 'energia ing circuit ot' `and `causing!` the deenergization ot release magnet SRM, which restores its armature to the normal position for en gag-ement with the arm 20 ,7. upon the coinpletion ot the. cycle. With automatic selector switch SlS'inV engagement with the first of the two contacts allotted to the jack 10 ofthe trunlrline L1, it will be seen that V.positive current is connected with the lirst,

second, fourth, fifth and sixth levels, while negative, current is connected withthe hrst contact ot the third lerel'only. lVhen the brush arm 207 engages the segment 210, a

circuit is completed/tor relay 205, which entends trom battery through the ring 200, brush arm 201, the segment 210, andthe winding ot relay 205 to ground. The

' operation ot' relay 205,A due to the formation ot this circuit. removes the battery connected to brush arm 204 of the selector switch SS. As the brush :11111207 successirely engages the' individual sending segn'ients 2l1lto 216, inclusive. ot the distributor, impulses ot current ot the polarity connected with such vsegments through the brushes ot theselector switch SS are successirely connected with the common signaling conductor P leading to otice X. When the brush arm 20T moves out ot engagement with the segment 210, the energizing circuit ot slow release relay 205 is opened and-when the brush arm thereafter engages segment 217, a circuit is formed to cause the energization of relay 203, which extends from battery through the lring` 206, the brush arm 207, the segment 217 and the winding ot relay` 203 to ground. Release relay 203, in operating, opens the locking `circuit ot relay 201,*and such relay releases. Relay 205 is inade slow in releasing so that its normal contacts remain open until after the opening ot the contact ot relay 203. As the arm 207 disengages the segment 217, relay 203 is deenergized. lWhen the brush arm 20'? engages the restoring segment 21S, negative current isconnected with the signaling conductor l). The .switch SS is now in position to be seized by another trunk line or i trunk line terminal, since the trunk line terminal ot jack 10 is disconnected therefrom and the sending distributor is again its-normal position.

i The'conncction ot the positive current through the start segment 209 with the lower winding ot such relay and the artiiicial line associated therewith to grcuinl` and by another path through the upper winding of relay 219, the conductor P, both windings ofthe differentially polarized rclay 319, and the artificial line at the oiiice X to ground. rlhe operation ot relay 319, causes the operation ot release magnet RRM associated with the receiving distribu- `tor R at otiice X. The circuit for such magnet may be traced from battery through the' alternate Contact of relay 319, the segment 320, the brush arm 321. the segment and the winding' ot release magnet RTM to ground. rlhe attraction ot' the armature oit the release magnet releases the brush arni 321, which is thereupon rotated through a complete cycle in` synchronisin withA theA sending distributor S at otlice lV, at the end ot which it is stopped in its normal position by the latch on the armature ot the release magnet which has again assumed its normal position. As the brush arni 321 mores out ot engagement with the segments 320 and 322, the release magnet lllihi is dcencrgized thereby permittingthe r oration ot its arniature to its normal position to arrest the motion otl the brush arm 321 when it completes its rotation. TWhen the brush arm engages the segment a circuit is completed tor relay 324, which e3*- tends trom battery through the common ring 325. the brush arm 321. the segment and the winding of relay 32a! to ground. The closure ot the contact of relayr324r, prepares the locking circuits tor the Various relays 320 itin ' `to 331, associated with the receiving seg-H ments 311 to 3160i' the distributor 1t. The

armature of thediferentially polarized re- ,.lay 319, remains in its alternate position as long as positive current is connectedwith kthelfother .end of thecoininon conductor P and is restoredto its normal position Whenever a! negative `current is connected with e theother end of such conductor. The brush arms 207 and 321 are being rotated at the vsaine time and in synchronisin with V,each

other so that while thebrush207 is engaged with the individual seiidingseginent 213, the armature of relay 319, is restored to its normal position and brush 321 engages the individual receiving segment 313. A cir-y cuit is then completed which extends from battery through the normal contact of relay 319, the common receiving segment 333, the brush 321, the individual receiving seg- ,ment 313, and the lower winding of relay 328 to ground. The latter relay operates over this circuit and locks due to an obvious circuit, dependent upon the the venergization of relay 3211.V The closure of the lower con-` tact ot'relay 328 causes the operation of relays 334` and 335 over a circuit extending from battery through the windings'of such relays in series and the lower alternate contact of relay 328 to ground.l lNhenthe brush farin 321 engages thesegments336 and 337,

the signal-receiving relay associated with the trunk line jLl at oiiice X, operates over a circuit extending from negative batteryV through the lower normal Contactv of relayv V'331, the segment 33.6,y the brush arm 321,

the segment 337, the normal contact of relay "330, the, lower normal contact ot relay 338,

thelower alternate contact of relay 335,the upper normal contacts ofV relays 339 and 340,

vthe signal-receiving conductork E, and the left-hand winding or' signal-receiving relay 4:00 to ground. RelayV 400 operates and locks through its rightdiand winding, the polarity of thev current through the two windings Y of such relayvheing the same. The signal-'re` ceiving relay 4101 also operates, since its righthand winding is included in parallel with the left-hand winding of relay 400 by virtue Y Y of thel contact of slow-release relay 402.

However, relay 401 does not lock due to the deenergzcd condition of slow-release relay403'. The energization of relay Z101 does not at this time )ertorin anv useful funcf .f

tions. The closure oit the left-hand contact or relay s100-places the winding of super-V visory relay 404 Vin bridge across the con` i ductors of the trunk line L1, vwhile the closure of the right-hand alternate contact of relay 100 causes the illumination of lamp e105 over a circuitextending from battery through 'the right-hand alternate Contact of relay 400, the lower normal contact of re lay 4.06, and the lampV L105 to ground. WhenA `the brush 321 disengages segments 336 and lmentV 341causes the release oitl relay 324so Vthat the locking circuit `ot relay 323l is Ll and secure troni theoperator atoitice l/Vj Y vplug 500 of thetoll switching trunk Q into 337, the energizing circuit ofielays Ve100* andY e 4.01 is opened, causingtlie deenergization ot" NVrelay 401, Sl'ow-relezltse relay 402.7s then energized overa circuit extending from hattery' through the rightehandraltei'iiatejcon-f To tact of Vrelay 4f00,fthe lower normal contactA or relay 4106, and the windingot Y slow-release opened and relays V334: `,and 335V are fdee'ner- Y gized. All apparatus associatedrwith the; Y, automatic selecting switch SS, the sendingfY vdistributor S,fjthereceiving distributor and the receiving circuit' atfotiice X, is-now479 in normal condition sforthat it may he ein-V ployedVV in connection with any other trunk Vline circuit. .The lighting ofthe lamp 105 serves as a guardsignal to the operator at the Vterminating position of ottice X; indieating that .the .operator at the originating otiice W connected the toll'V cord circuit VO with, the trunk'linecircuit L1.;Y`

The operator at otticeXmaynowy connect v hei' head set. indicated: OT. toftheline theV desired Vnumherf She mayV also 'coininu-A nicate with the toll switching'trunlr'fopera- Y tor at'ot'rice X, heforelwhom the telephone linecircuit T terminates over an order wire no (not shown), to secure an assignment oi 'toll switching trunk.` Illhetoll switching operator at the' otlice .X Vinforms the incomeV ing orreceivingoperator at the same ocov that the toll switching trunlr Q, leading, loe-` tween such positions of the Votiice Xfshould be employedfor extending the connection to the Vwanted lineV circuit YT. Immediately upon assigning .the trunk Q'ifor Vvthis purpose,'tlie tollswitchingoperator inserts they the jack 501 ofthe desired line circuit T.

The cut-oft relay 502 of the line circuit and the'sleeve relay 503 of the tollswitching trunk@ thereupon operate over an obvious circuit. The operation of relay502 per- `torins its usual function in removing the line relay 504 from its associationwith the 1 line conductors and thereby prevents the dis play of the usualline signal lamp 505 upon the answer of the called party. 'Y The open-V` 3Q ing ot the right-hand normal contact ot relay 503 disconnects the usual operators telephone circuit testing arrangement from the tip conductor ot the cord circuit With which a test is made, by placing such tip conductor in contact with the sleeve of jack 501 prior to the insertion of the plug 500. rlhe closure ot' the right-hand alternate contact oit relay 503 completes the continuity of the tip conductor ot the trunk circuit, While the closure ot the lett-hand alternate contact of such relay causes .the illumination ot lamp 506 over a circuit extending from battery through the lamp 506, the lett-hand alternate contact ot relay 503, the resistance 50T,

andthe normal contact ot relay 508 to' ground.

@owned/0a of the tim/alc 'circuit LZ with the toll switching trtmc circuit The operator at otce X, upon observing the lighted condition of the lamp 405, inserts the plug 407 of the trunk line L1V into the jack 509 ot the toll switching trunk Q. Relay 408 thereupon operates over an obvious circuit. The operation of relay 408 causes the ope ation ot' relay 406 over an obvious circuit, the opening of the lower normal contact of relay 406 extinguishingy the lamp 405 and releasing slow release relay 402. The opening ot the upper normal contact ot relay 406 disconnects the usual operators telephone testing set from the trunk line L1 and the closure of the upper alternate contactrot such relay completes the continuity ot the tip conductor ot the trunk line L1.

The vsupervisory relay 404 ot the trunk line L1 and. relay 508 ot the toll switching trnnl; Q, operate over a circuit extending :trom battery through the lett-hand 1Winding ot relay. 508, the lett-hand normal contact ot relay 510, the ring contacts ot jack 509 and plug 407, the lower normal Contact ot relay 400, the lower normal Contact ot relay 410, the lett-hand alternate contact oll relay 400, the Winding oit relay 404, the upper normal contacts oit relays 410 and 400 in series, the upper alternate contact ot relay 406, the tip contacts ot plug 407 and Vjack 509, the right-hand normal contact ot relay 510, and the right-hand Winding of' relay 508 to ground. The energization ot relay 508 extinguishes the lamp 506 at the toll switching trunk position. gization ot supervisory relay 404 causes the operation of sloW-to-operate and release relays 411 and 412 and relay 413, the energizing circuittor relay 411 extending from battery through the Winding ot relay 411, the alternate contact of supervisory relay 404,

and the normal contact of marginal relay' 414 to ground. Relay 412 operates over a circuit extending from battery, through the `grounded battery.

rlhe enery Winding and right-hand normal contact of said relay,-the right-hand contact ot relay 415, the outer right-hand normal contact of relay 416, the alternate contact ot the supervisory relay 404 and the normal contact ot relay 414 to ground. lnasmuch as the relay 412 is slowto operate, a circuit will be established'tor relay before the armatures ot' relay 412 are attracted, which circuit is traceable lrom ground, through the Vnormal contact ot' relay 414, the alternate contact of relay 404, the outer right-hand normal contact-ot relay 416, the right-hand contact of relay 415, the lett-hand normal Contact ot relay 412, the inner right-hand normal contact and Winding oit relay 413, the inner lett-hand contact ot relay 415, the start conductor X and the Winding ot start relay 341 oit the sending distributor S to Y Relay 413 energizes and locks through its make-betore-breal; Contact and, in so doing, disconnects the ground at the marginal relay 414 from the common start conductor X. However, the ground on this conductor is now maintained through the locking circuit tor relay 413. Relay 412 is locked over a circuit traceable `trom battery through the Winding and right-hand alternate contact ot said relay, the lett hand Ynormal contact ot' relay 417, the outer right hand normal contact ot relay 416, the alternate contact of relay 404 and the nernial contact ot relay 414 to ground. The individual signal control conductor A10 grounded by the closure ot the outer letthand alternate contact of relay 413. The

energization ot relay 413 causes the operation ot relay 418 over a circuit extending from battery through the right hand alternate contact of relay 400, the right hand ,normal contact of relay 419, the Winding ot relay 418, the lett hand normal Contact of relay 420 and the limer lett hand alternate contact oit relay 413 to ground. The

operation oiI relay 418 closes a circuit 'lorA relay 420, but this relay is shunted through contacts oit relays 413 and 416. Upon the grounding of the common start condiuiftor X as previously described, the sending apN paratus at oltice X functions to transmit a combination ot current impulses over the common signaling path P to the oliice WY, Which is similar, in character to that transmitted from the office W to the ottice X in connection with the lighting ot the guard lamp at the office X. The common start relay 341 operates in response to the ground- `ing oit the start conductor X and a circuit tor motor magnet MM is completed. The motor magnet MM is of the ordinary seltinterrupting type and advances the various brush arms o the'selector switch SS until Vthe brush arm 342 engages the conductor lll) lili

ie i

above-mentioned operations of the relays. Uponengaging such conductor relay V343 operates to discontinue the operation oi the motor magnet and the rassociated brush iarms,tlie relay 343 locking over an obvious circuit including the contact ot relay 344` V\7hen the brush arm 342 engages the conductor A10, the brush arm 345 is in engagement .with the release conductor BlO so that upon the operation oi relay 346 alter the distributor S has started its revolution,

Vcommon start conductor Vcurrent flows over conductor Bl() ,trom the whereupon the latter relay operates over ar circuit through the Contact of relay 41S to ground at the inner right hand normal contact or" relay 416. When the Vrelay 343 operates, the release magnet SRM, energizes to release the brush arm 353 which then Vmakes a complete revolution. During this 30 revolution, the brush arm 353 successively engages segments 347 to 352 and a series ofY current impulses is thereby transmitted over thecommon signaling path P in accordance with the polarities connected to said segments through the brush arms of n the selector SSI.V

The sending distributors S', during the completion ol the cycle of the brush arm 353, functions in `exactly the same manner as the sending distributor SV at the ollice lV, which has been described iu the'transinission of the signal to light-the guard lamp at the ofliee X. Therefore, the impulses ol' current which are arranged in the saine manner as previously--described,

are transmitted over Vthe common signaling conductor P to the oflice lV, andare re-V ceived theieat bythe differentially polarized relay219. The receiving distributor R 1 functions in the saine manner as distributor R', aspreviouslyl described, to selectively operate certain relays and thereby select the Signal-receiving conductor E and to send .Y thereover an .impulse of negative polarity.

i segments 237 and 233, the lower normal con-V is the brush arm 221v rotates, relay 222 is lirst energized and'then as the segments 223 to 22S are engaged, circuits are prepared for each of the relays 229 to 234; However,-

only-relay 231 operates and locks under the control of relay 222. Relay 231 operates relays 235 and 236. When the brush arm 221 enga'es segments 237 and 238, acircuii4 is established from negative `battery through the lower normalcontaet of relay 234, the

and causes the v `remain tacts of relays vand 239, the lower alternate contact of relay 236 andA the upper nor .7

mal contactsof relays 240v mdp ,to thconductor E', f I

The current of negative polarity traversing the signal-receiving conductorlllows throu h the. lett-hand'windino 0iE the sie'- nal-receiving relay 27, causing the opera-j" tion of such relay. Relay 29 doesV not operate due tothe energizationol relay l28 which Y 5, l I

operated when relay 13 was energized; Re-

lay .27 locks since the'polaiities of thecurf rents flowingV throughthe lenergizing vand locking windings thereof` are such that. the relay is maintained energized. Theenergization of relay 27 releases relay 28A'bi`it this relay d oes not close its Contact untilfaftei1 the impulse has beenV transmit-ted `overl con'- ductoi' E. The reg-,ristanceV 26"-isA connected in a branch circuit around the winding ot relay 11, the branch circuit being. trzjiceable fromV ground through the ynormalcon'tactY of relay 29, the left-handalternate contactV n' of relay 27, .the resistance 26,the inner righthand contact of relay 13, to the sleeve contact ofjack 10. By the introduction ot this ,Y

branch circuit, the vamount Vot current Vflowing through the winding ofvmargina'l super-l visory relay 6 is increased suiiiciently to .Cause the operation of; suehj Vrelay and t0 cause the subsequent lighting of the supervisory lamp 7 o-veran obvious circuit.V As/V soon as the set ofV impulses is transmitted from the oliice X, to the votlceV lVand' re-f ceived thereat,all the apparatuseinployed to its normal condition in a manner similar to thatdescribed' in coiinectio'nwitli'the ini- Y pulses transmitted in response to' the inser- Y tionot the plug 1 into the jack 10. It will be borne in'mind that relays 418 a.nd420jV energized since relay 40() isv Astill li 2vlocked.

Tteroperarornatoyce W [tolerates Hic l rin gng key;

YThe operator at oliice lV, observing the,y

lighted condition of the supervisory lamp 7, Y is advised therebythat the connection has Y* been established with the-telephone line circuitfl at the ofiiceX.. The ringing key 2 is then actuated, which eoiiipletes'a circuit from the source of ringingcurrent through"Y the lower alternate Contact ofley 2, the rii'ifgr contacts of plug 1 and jaclc10`,'the lower normal ,Contact orv relay `16, the condenser 13, the'winding` of ringing response relay .17, the upper normal Contact of relay 16, the Y tip contacts of jacklO and plug 1 andthe lupperalternate Contact otkey'2 to ground.

The ringing of current flowingV overrth-is path causes the voperationfof relay`17 vwhich also causes the 'operation of' slowrelease relaf.T 25 over an obvious circuit. YYYRelays 17 in the sending of such impulses is restored 10U- The operator at 077%@ 'W rele/ses he rengz'ag leeg/ Upon the restoration of the ringing key 2 ot the operators cord circuit O to its normal position, relay 17 releases, causing the deenergization of relay 25. A ground connection is thus completed for the common start conductor X, which extends from the Y outer right-hand alternate Contact orn relay 34, through the outer right-hand alternate contact et' relay 24, the right-hand normal contact ot relay 25, the inner lett-hand contact of relay v35, to the start conductor X. A ground connection is also completed for theindividual signal-control conductor A10, which extends from ground through the outer lett-hand alternate contact ot relay 24, the left-hand normal contact ot relay 25, the outer left-hand normal contact ofrelay 35, the outer right-hand alternate contact oit relay 12, to the individual signal-control conductor A10. The grounding of these two conductors, causes the operation ot the sending distributor S and the associated selector switch SS to function to send over the common signaling path l) from the o'ltice W to the office X, a combination et impulses similar to that transmitted in response to the connection ot the cord circuit -Owith the j ack 10. These impulses are received by` the common receiving apparat-usv including the receiving distributor R andthe various 'associated locking and selecting relays, and, therefore, selectthe signal-receiving` conduct-or E as in the previous case, and thereupon an impulse of negative polarity ot current is transmitted over such conductor. This impulse of current being of the same polarity as that which originally flowed through the left-h and winding` ot relay 400, produces no etlect on such relay. However, due tothe deenergized condition of relay 402, such current also flows through the right-hand winding of relay 401and causes its energization. Relay 403 which was mainl tained in an energized conditionV over a circuit extending from battery through the right-hand alternate contact ot relay 400 Vand the normal contact or" relay 401, deenergizes upon the energization of relay ,401, but due to the fact that relay 403 is slow to release, a vtemporary locking circuit is pro-v vided for relay 401 which includes the letthand winding and left-hand alternate contact of relay 401 and the alternate contact ot relay 403 to ground. lVhile relay 401 is v operated, a circuit is termed from battery through the right-hand alternatecontact of are 'maintained operated while the relay 400, the right hand alternate contact, of relay 401 and the winding of slow-release rela-y 421 to ground. Relay 421, in operating, closes an obvious circuit tor slow relay 422. Vhile relay 421 is operated a circuit is completed for ringing relay 410, which extends from battery through the winding o't` relay 410 and the right-hand alternate contact ot relay 421 to ground. Due to the slow release nature of relay 421, as well as relay 403, relay 410 is maintained operated for an appreciable time after the release ot the ringing` key at the otlice Wl. During such period a circuit is completed from the source of ringing current through the lower alternate contact of relay 410, the lower normal contact of relay 409, the ring contacts ot plug 407 and ack 509, the winding ot ringing' response relay 511, the tip contacts of jack 509 and plug 407,v the upper alternate contact ot relay 406, the upper' normal contact ol? relay 409, and the upper alternate contact ot relay 410 to ground, Ringing relay 512 thereupon operates over aV circuit extending from battery through the lett-hand winding of relay 510, the winding ot relay 512 and the contact of relay 511 to ground. Relay 512, in operating, completes'a circuit tor the ringing current which extends from the source ot such current through the righthand alternate contact of relay 512, the ring contacts ot plug 500 and j ack 501, the winding ot' the signaling bell at the station on the line circuit T, the tip contacts of jack 501 and plug 500, the right-hand alternate contact ot relay 503 and the left-hand alternate contact of relay 512 to ground. The bell at the subscribers station is thereby operated to signal subscriber that a call await-s an answer. As soon as the slow release relay 421 is entirely deenergized, relay 410 vrcleases and removes the current from the trunk line circuit L1 and theconnected toll switchingtrunk Q so that relays 511 and release and remove the ringing` current 'trom the telephone line circuit T. Thus upon each actuation of the ringing key, the lollowing release of such key transmits a combination o't impulses oit current te the oliice X and causes the functioning of .apparatus thereat to apply ringing current through the toll switching trunk Q to the selected line circuit T for an appreciable predetermined interval.

T71@ subscriber at the str/tion on Hz@ dep/zione Zane cercati T ramones the recez'oer from l 27m switch/0070.

lltl

hand Vnornial contact of relay V512, the ring contacts of plug 500-and jack 501, the telephone apparatus at the station on theline circuitT, the tip contacts ci jack 501' and plugOO, the right-hand alternate contact o relay 503 and the left-hand nornial contact of relay 512 to ground. VRelay. 513, in operating, causes the energization et relay 510 over a`V circuit extending troni battery Vthrough the lett-hand Winding olf relay 510,A the contact .of supervisory relay 513,

the right-hand Winding of relay 510 andV the alternate Contact of relay 508 to ground.`

' gization of the supervisory relay 0l due to the opening of the circuit thereof by ldisconiiecting the windings of relay 508 troni trunk L1. Relay 4104, in releasing opens the circuit lof relay 4:11 but this relay is ,very

slow to releaseand. therefore does not iinl di) inediately open its alternate contact. ii circuit is therefore established for the sloiv toV release relayed-23 extending troni battery through the Winding of said relay, the alternate contact of relay 111, the norinal contacto'f relay Llila and tlienorinal contact of relay'llll to ground. The release of relay 404' also opens theloclring circuit for relay 412 which -is slightly slow in releasing,

' said circuit extending through the outer Vright hand normal contact of relayV 4,16.

lWhen relay VIi117 is'conipletely released, a Vcircuitis established for relay 416 LWhichezr-V tends froinbattery on the start conductor Y v ytran-sniission ci; such inipiilses `1re X Vthrough theouter leftliand contact of relay 415, the Wiiidingfoii relay 416, the

' the norinal contactsof relays 411,` i041 and.

outer right hand iioriiial Contact or' relay 413, the right-hand contact of relay 420 and 41a. Relay 416 energizes and locks .through its right 'hand alternate contact. Therenioval of ground rointhe inner right han-d normal contact or' relay 44:16 causes the release of relays t118 and 420, RelayV 416 in closing its left-hand Contact, grounds theV individual signal control conductor fCl-O, While vthegconiinon start conductor X is grounded throughthe Vouter left-hand con,- tact of relay 415, the lWinding and right hand alternate contact of ielaydlt.y lThegrounding of the start conductor X, as in Y the previous instance described iii connection WithV the completion of' the transmission circuit, causes the ope-ration of the com? nion start relay 341 at the ollice X and the remainder of Vthe common sending apparatus theieat lto function in a inanner siinilar "conductor 13'10 at the ner (not shown), and the p Y line 1 circuit T terminating Vat the /oiliee Q Asuch connection incliidingg` the trunk line Ll The submitter ref to that described in? theV previous instance.

However, the motor magnet 'MMf continues in its operation until tliebrush arni 342 ond of the contacts'on the bank iasscciated Vwith the brush arniBlQ kwhich are allottedv vto the terminal or jack 1 0 of the trunk line L1. In this insta-nce, when the brush arni of negative polarity are sent kbythe Vsend-` ing distributor S and thesek impulsesV are received by the ditlerentially polarized lrelay 2.19 and the receiving Adistributor R at the Y oilice lll in the manner'describedyto select the signal receiving Yconductor 'E vat the v latter oiiice. Relays Q31 and 23% are op-V erated bythe negative impulses transn'ii-t-` ted in a ina-nner ythatyill,beunderstoodV from previousdescriptionso that the inif `pulse of currentivliich iloiis'- over the zsignaling conductor E" at the silice WV is otpositiive polarity, and clue .toA the arrange nient of the windings ion the signal-.receiving relay .27, Acurrent of this polarity dit-V Y 'ferentializes and causesV saidv relay 'te re# lease. Although the current flows through the left-hand Winding` of relay 29no inaterial effect is produced Vthereby."Upon i the release of relay 27, relay 28 is again energized to disconnect thesigna-lreceivf relay -6` releases andv `eXtingui-shes the su Y pervisory lainp 7 to inforintlie operator that' the desired subscriber responded tothecall. fr 'fr Upon the sendingv of the iinpulses over:V

the coinnionsigiiali'ng path l), senr-linni and receiving apparatusassociated with the no rinal, as previously .describedj Y -nection of battery through -arni -v t tionf attpulses have been transmitted. eration of relay il-15in restore the ,re f

.li hay-e been used in starting the transinission et the ii Y The connection is Athu the cord circ/int@ to" A, phone cir-cuit koi: any paV beV connected in the neural lllrneivn :nal

and the toll sivitchingvtrunl; ,czireuit'G gres receinm u Y szmtcfzfilooc. Y .At the conclusion .ot 'the conversation the subscriber `at the station on'the linecircuit T restores the receiver tothe switcliliook,1 releasing supervisory relay 513 ,of the trunk`l` station on the v the circuit ot relay 510.

circuit Q, which relay, in releasing, opens Relay 508 is thereupon connected in `circuit with the supervisory relay 404 of the trunk line L1 to cause the energization of the latter relay. The energization ot supervisory relay 404 causes the energization of the relays as mentioned in connection with the establishment ot the connection between the trunk line L1 and the toll switching trunk Q. Such operations also ground the signal control conductor A10 and the common start conductor X. In response to the Vgrounding ot' these conductors, the common sending apparatus at oliice X functions in exactly the same. manner as previously described, to send the combination ot impulses over the common signaling path l? to the oiiice W, where such impulses are received to cause the selection of the signal-receiving conductor E and to transmit thereover an impulse ot negative polarity. This impulse ot' current causes the operation ot relay 27, owing through its lett-hand winding, such relay immediately looking through its righthand winding. The resistance 26 is again placed in parallel relation with the winding ot relay 11 to cause sutlicient current to tlow through the branch including' the windL ing o'l' marginal supervisory relay 6, thereby illuminating` the lamp '1" over an obvious circuit. As in the previous instance, upon the transmission ot these impulses all oi' the individual and common sending apparatus and the common receiving apparatus is restored to normal.

The operator at office W disconnects the toll coral circuit from the tru/n70 Zane circo/ft' Z1.

The operator at oiiice lV, upon observing the lighted condition of the supervisory lamp withdraws the plug 1 from the jack 10, causing the release of relays G and 11. The release ot' relay 6 opens the circuit of 'and extinguishcs the supervisory lamp 7; the release of relay 11 causes the release of relays 19 and 24. The conductor X is thereupon grounded through the outer righbhand alternate contacter relay 34 and the righthand normal contact ot relay 24. The deenergization ot the above mentioned relays also `grounds the signal-control conductor C over a connection which may be traced from ground, through the left-hand normal contact ot relay 24, the outer left-hand alternate contact ot relay 34, and the left-hand alternate contactot relay 13 to the conductor C10, relays 12, and 13 being maintained en ergized through the inner left hand alternatecontact ot relay 34. Thus the second of the two contacts associated with brush 202V ott the selector switch SS, which contacts are allotted to the jack 10 of the trunk line L1, is grounded.

The motor magnet MM thereupon functions when the start relay 200 is energized by the grounding ot the common starting conductor to advance all ot the brushes of the selector switch Si@ until the brush Q02 engages the contact connected with the grounded signal-control conductor C10, whereupon relay 201 operates and stops the motor magnet.. The operation of the other sending apparatus at the oiiice lV will be the same as that previously described in connection with signaling impulses originating at otiiee W, except that the combination of impulses sent over the common signaling conductor l) to the oliice X, diii'ers trom that succeeding the insertion ot the. plug` 1 into the jack 10, in that the polarity ot the impulse sent over the selected signal-receivinpl conductor at the oiifice X is positive rather than negative. The impulses received at the oiiice X are distributed, as in the previous cases, by the receiving` distributor lt. and select the proper signal-receiving` conductor E, as previously mentioned. This inipulse of current flowing through the letthand winding of relay 400, is of such a polarity that it dilierentializes such relaj.v and causes it to release. The. closure of the right-hand normal contact of relay 400 causes the illumination or" lamp 405 over a circuit extending trom battery through the normal contact ot relay 400, the lower altenate contact ol` relay 40G, and the lamp 405 to ground. The illumination ot lamp 405 serves as a disconnect signal to the terminating operator at office X. 'llhe opening' ot the left-hand alternate contact ot relay 400 opens the bridge across the trunk line L1, which includes the winding ot supervisory relay 404. ylhe battery supply relay 508 ot the trunk circuit Q thereupon releases and t ie lamp 506 is illuminated betere the toll switching operator over a circuit extending from battery through the lamp 506, the lett-hand alternate Contact ot' relay 503, the resistance 507, and the normal coutact of relay 508 to ground. The illumination ot the lamp 506 serves as a disconnect signal to the operator at the toll switching` position ot the ofiice The terminating and toll switching trunk operators at the oiiice X, in response to the signalfiz oirsplayed by the lamps 405 and 506. remove the plugs 407 and 500 reslwctively Atroni the jack 00 and 501, thereby restoring all ag'njarzatusl; to normal position. as shown in the drawings.

The subscriber mi the stat/'on on Hic M7@- pzonc Zinc @iwi/xfa T 'zu-n-nf/zffng or ortz'rc X recalls the operator of oyjifrc W.

Should the subscriber at the station on the line T, atter the completion ot a conversation with the oliice il over the truuk line Ll and the toll switching trunk Q,

Cil 

